This invention relates to a needle bar positioning apparatus for a multiple needle tufting machine, and more particularly to a tufting machine having dual shiftable needle bars.
Heretofore, in the production of tufted fabrics, distinctive patterns, such as various zig-zag patterns, have been formed in backing fabrics by transversely or laterally shifting the needle bar, or by shifting the backing material support beneath the needle bar, needle-gauge increments for each stitch, in accordance with a predetermined pattern.
However, tufting machines for forming patterned tufting pile fabrics utilizing shiftable needle bars have only utilized a single needle bar. Examples of such a single-needle bar shifting means actuated by pattern cams are shown in U.S. Pat. Nos. 3,026,830 of Bryant et al, Mar. 27, 1962, and 3,109,395 of Batty et al, Nov. 5, 1963.
The U.S. Pat. No. 4,173,192 of Schmidt et al issued Nov. 6, 1979, discloses an electrohydraulic needle bar positioning apparatus for transversely shifting a single needle bar by hydraulic drive means controlled by electronic pattern means.